The molecular regulation of axillary bud fate determination and outgrowth into branch crown in strawberry involves BRC1

In strawberry, the axillary bud (AXB) can produce either an elongated stem called stolon giving a daughter-plant (asexual reproduction) or an inflorescence-bearing branch crown (BC; sexual reproduction). The AXB fate depends on node position on the axis and on genetic and environmental factors. Here, in Fragaria vesca, we addressed the largely unanswered question of how molecular factors determine AXB fate. To get insights into the mechanisms already at play in a morphologically indistinguishable (undifferentiated) AXB, depending on its fate, we combined the phenotypic characterization of AXB development throughout plant growth with the RNA-seq analysis of undifferentiated AXBs, using three different genotypes producing either BCs or stolons. Results allowed the identification of genes regulating AXB fate and outgrowth, among which was FveBRC1. Exogenous applied gibberellin failed to restore stolon formation in CRISPR/Cas9 brc1 mutants, which produce BCs instead of stolons, thus demonstrating that FveBRC1 is necessary for AXB determination into stolon. These original results provide new insights into the molecular regulation of AXB fate in strawberry and highlight the major role of FveBRC1, not only in repressing BC outgrowth but also in determining AXB fate.